STUDIES OF REGULATION IN E.COLI EXTENDED TO LYMPHOMAS

我们项目的目的仍然是了解糖皮质激素的作用 激素对基因表达的影响 我们正在调查两种反应： A中T淋巴瘤细胞的溶解和纤连蛋白的诱导 纤维肉瘤细胞系 到目前为止，我们对糖皮质激素诱导的淋巴细胞溶解进行了研究 用鼠淋巴细胞系。 近几个月来，我们扩大了 对人类急性淋巴细胞白血病细胞系CEM的研究。 我们有 研究了糖皮质激素抵抗的基础， 细胞系CEM-C1，已知含有功能性糖皮质激素受体。 用DNA-去甲基化剂5-氮杂-2 '处理CEM-C1细胞 脱氧胞苷高频率地产生糖皮质激素敏感的亚克隆 （约10%）。 这表明DNA甲基化是导致 用于灭活所需的“裂解”功能的表达， 这些细胞中的糖皮质激素敏感性。 我们已经跟踪了我们的观察，糖皮质激素增加10- 1， 20-HT 1080纤维肉瘤细胞中纤连蛋白生物合成速率的1倍。 使用人纤连蛋白cDNA克隆探针北方印迹，我们发现， 该探针与来自人的高分子量mRNA杂交， 地塞米松处理的HT 1080。 这种mRNA的水平要低得多， 在未处理的HT 1080细胞中，并且在CEM细胞中检测不到，CEM细胞不 产生纤连蛋白。 通过对细胞总RNA的“狭缝”印迹分析， 发现激素治疗后纤维连接蛋白RNA水平增加了16- 32倍， 治疗 此外，这种诱导被糖皮质激素抑制 拮抗剂RU 486。 这项研究表明，地塞米松诱导的 纤连蛋白生物合成的刺激是纤连蛋白生物合成增加的结果。 糖皮质激素受体介导的纤维连接蛋白mRNA的积累。 目前正在进行研究，以检查这种影响是否是由于 加快了转录速度 （丁）

The aim of our project remains to understand effects of glucocorticoid hormones on gene expression. We are investigating two responses: the lysis of T-lymphoma cells and the induction of fibronectin in a fibrosarcoma cell line. Our studies of glucocorticoid-induced lymphocytolysis have been done so far with murine lymphoid cell lines. In recent months we have extended our work to the human acute lymphoblastic leukemic cell line CEM. We have examined the basis for glucocorticoid resistance in a subclone of that line, CEM-C1, known to contain functional glucocorticoid receptor. Treatment of CEM-C1 cells with the DNA-demethylating agent 5-aza-2' deoxycytidine yielded glucocorticoid-sensitive subclones at high frequency (approximately 10%). This indicates that DNA methylation is responsible for inactivating the expression of a "lytic" function required for glucocorticoid-sensitivity in these cells. We have followed up on our observation that glucocorticoids increase 10-\to 20-fold the rate of fibronectin biosynthesis in HT1080 fibrosarcoma cells. Using a human fibronectin cDNA clone to probe Northern blots, we found that this probe hybridizes with a high molecular weight mRNA from dexamethasone-treated HT1080. This mRNA is present at a much lower level in untreated HT1080 cells and is undetectable in CEM cells, which do not produce fibronectin. By "slot" blot analysis of total cellular RNA, we found a 16-\to 32-fold increase in fibronectin RNA level after hormone treatment. Moreover, this induction is inhibited by a glucocorticoid antagonist, RU486. This study demonstrates that the dexamethasone-induced stimulation of fibronectin biosynthesis is the result of an increase in accumulated fibronectin mRNA mediated by the glucocorticoid receptor. Studies are currently in progress to examine whether this effect is due to an increased rate of transcription. (D)